The present invention relates to a silicone-polymer-modified vulcanized-rubber composition not based on silicone elastomer, for example for the production of windshield wipers. The present invention also relates to a process for the production of said vulcanized-rubber compositions, and also to a windshield wiper with wiper blades.
Elastomers and vulcanized-rubber mixtures are in particular divided into silicone-based and non-silicone-based compositions.
Among the known vulcanized-rubber compositions not based on silicone elastomer, for example for the production of windshield wipers, are inter alia vulcanizable formulations which comprise natural mixtures, an example being unvulcanized rubber, or synthetic mixtures, examples being polychloroprene or unvulcanized ethylene-propylene-diene rubber (EPDM) and ethylene-propylene rubber (EPM), and also mixtures of these. Other materials used for wiper blades are silicone-based elastomer compositions, the aim being to achieve improvements in the sealing with respect to the windshield, and improvements in resistance to temperature change. Examples of compositions used hitherto are disclosed inter alia in U.S. Pat. No. 5,283,927 or in international patent application WO 02/096992. However, a feature common to these compositions, with respect to their formability and processability, is that, in order to achieve adequate processing properties and mechanical stability, they have to be provided with specific reinforcing fillers and extender additives. Examples of these structurally reinforcing fillers are calcined or precipitated quartz and amorphous silica, and examples of suitable extender additives are ground quartz and celites or limestone-containing particles. However, specifically the use of extender additives has some attendant disadvantages with respect to rapid wear on the extruder machinery, impairment of water-repellent properties of wiper blades produced from said compositions, and reduced long-term stability.
In addition, the known silicone-based vulcanized-rubber compositions need a markedly longer vulcanization time in comparison with the vulcanization times exhibited by extruded or injection-molded non-silicone-based vulcanized-rubber mixtures based, for example, on unvulcanized natural rubber, unvulcanized chloroproprene rubber, EPDM, EPM, or mixtures of these.